Reliving the Whitney Survey…150 years later

October 26, 1862: San Francisco

Safely back here again I will go on with…a few more words on the great interior valley of the state, that of the San Joaquin and the Sacramento.

This great feature is a vast valley, often thirty to forty miles wide, a perfect plain enclosed by high mountains on both sides, its only opening, the Straits of Carquinez, being less than a mile wide. One can start on this plain, near Shasta, and travel southeast four hundred and fifty miles in a nearly straight line, without crossing any hill of any considerable height—that is, if a road is run near the rivers.

The extreme north end rises in a table-land a few hundred feet high, but the valley does not taper to a point—it is cut off nearly square, where it is at least thirty miles wide, by the mountains that extend across the north part of the state. But the eastern edge is modified by a range of hills that stretches east from Lassen’s Peak, down into the valley, way to the river, near Red Bluff, so that the upper end of the plain spreads out above it, something like a letter T. Now these hills mentioned are mostly of lava and need more than a passing notice, for they impart features to the landscape so unlike anything else that I must make these preliminary explanations so that you may understand what I will have to write for some time to come.

Lassen Peak aerial view; by dsearls, on Flickr

Lassen’s Peak, and in fact, that whole part of that chain, like Mount Shasta, is a gigantic extinct1 volcano, perhaps about twelve thousand feet high—a volcano not only much higher, but vastly greater in every respect of magnitude and effect than Etna. It is flanked by a considerable number of smaller cones, old volcanoes, from one thousand feet high, up to that of the main peak itself, many of these cones being much higher and greater than Mount Vesuvius.

Here, in a former age of the world, was a scene of volcanic activity vastly surpassing anything existing now on the earth. The materials from these volcanoes not only formed the mountains themselves and covered the foothills, but also came down on the plain for more than a hundred miles. Sometimes volcanic ashes covered the whole region many feet thick, then sheets of molten lava would flow over it, hardening into the hardest rock, then ashes and lava again. Thus were formed beds of enormous thickness, regularly stratified, descending with a gentle slope toward the Sacramento River, and even crossing it in one place near Red Bluff.

But all volcanic action ceased ages ago, and the snows and rains falling on the high lands about Lassen’s Peak formed streams which radiate from it. They have worn deep canyons, channels, in this lava, often a thousand feet deep, but generally less. Between these are table-lands, sometimes strewn with loose bowlders of lava, at others showing a surface of nearly naked lava with only enough soil to support, here and there, low cragged shrubs and a few herbs during the wet parts of the year….

By the way, I have forgotten whether I have given you the height of Mount Shasta—it is 14,440 feet, the highest land yet measured in the United States. I feel proud that I took first accurate barometrical observations to measure the highest point over which the Stars and Stripes hold jurisdiction.